Comparisons of Actual Fish Observations with Simulated Suitable Fish Habitat in Minnesota Lakes

The purpose of this study is to relate simulated water quality with fish presence observations. The typical seasonal patterns of water temperatures and dissolved oxygen concentrations in twenty-seven classes of Minnesota lakes have been simulated by calibrated models and related to observations of three fish guilds i.e, coldwater, coolwater, and warmwater fishes. Data from 3002 lakes were available in the Minnesota Department of Natural Resources lake database. Water temperature and dissolved oxygen criteria derived from a very large USEP A fish-temperature data base and dissolved oxygen observations were used to define and link simulated water temperatures and dissolved oxygen conditions to suitability of habitats for various species of fish. One-dimensional, dynamic models driven by 25 years of observed weather data were used to model daily water temperature and dissolved oxygen as a function of depth. The lakes are categorized according to surface area, maximum depth, and Secchi depth as a measure of trophic state. Good agreement between fish observations and numerical simulations of fish habitat defined by water temperatures and dissolved oxygen concentrations was found.